Out-of-bounds write in Linux kernel - CVE-2026-89834

Vulnerability identifier: #VU150446

CSH Severity: Low

CVSS v4: 0 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-89834

CWE-ID: CWE-787

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to perform out-of-bounds I/O.

The vulnerability exists due to incomplete iteration over active curseg types in free_segment_range() when shrinking an F2FS filesystem. A local user can initiate a filesystem shrink operation while active in-memory curseg types reside in the target range to perform out-of-bounds I/O.

Non-persistent in-memory curseg types, including CURSEG_COLD_DATA_PINNED and CURSEG_ALL_DATA_ATGC, can remain in the truncated range.

Linux kernel
Debian Linux
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux (Debian package)

Install security update from vendor's repository.

linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17
linux (Debian package) - update to 6.12.111-1

• https://git.kernel.org/stable/c/3b85edf3391f3e1f624f409a7d2d239885f567b7
• https://git.kernel.org/stable/c/8ec06f50ddd8d201bd7e55b896ae28ed9d4cb7d1
• https://git.kernel.org/stable/c/b8ae1228c153622afa71a179c9d4dc268117e0f0
• https://git.kernel.org/stable/c/b9776094aa7118e8e5dfdcd791ffc8330c5ca408

• Out-of-bounds write in Linux kernel f2fs
• Debian update for linux
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more